Chemical Equations

reactants products

reactant- starting substance in a chemical reaction

product- substance formed in a chemical reaction

= yields, gives you, produces, goes to

**Law of Conservation of Mass holds true here

mass of reactants = mass of products

-the states of matter can be indicated after the substance

(s)=solid (ℓ)=liquid (g)=gas (aq)=aqueous

= reversible reaction

catalyst- substance that speeds up the rate of a reaction without being used up in the reaction

**written above the arrow

ex- Pt ∆ = heat applied

**Remember H O N Cℓ Br I F

skeleton equation- chemical equation that is not balanced

ex- Write a skeleton for the following reaction:

solid iron reacts with oxygen to form solid iron (III) oxide

Fe(s) + O2(g) Fe2O3(s)

Try these:

1) solid sodium hydrogen carbonate reacts with hydrochloric acid to produce aqueous sodium chloride, water and carbon dioxide

2) solid sulfur burns in oxygen to form sulfur dioxide

3) solid potassium chlorate forms oxygen and solid potassium chloride in the presence of catalyst manganese(II) oxide

Answers

1)NaHCO3(s) + HCℓ(aq) NaCℓ(aq) + H2O (ℓ) + CO2(g)

2) S(s) + O2(g) SO2(g)

3) KCℓO3(s) MnO O2(g) + KCℓ(s)

Balancing Equations

-each side of the equation (reactants and products) must have the same # of each element

-some may already be balanced

-must be lowest whole # ratio

-balance by putting coefficients in front of compounds

Types of Chemical Reactions

1) Combination/Synthesis Reaction

-two or more substances combine to form a single substance

reactants- two elements or two compounds

products- always a compound

ex- 2K + Cℓ2 2KCℓ

ex- SO2 + H2O H2SO3

Try these!! Don’t forget to balance!!

a) aluminum + oxygen

4Aℓ + 3O2 2Aℓ2O3

b) copper + sulfur (two possible reactions)

2Cu + S Cu2S or Cu + S CuS

c) beryllium + oxygen

2Be + O2 2BeO

d) strontium + iodine

Sr + I2 SrI2

e) magnesium + nitrogen

3Mg + N2 Mg3N2

2) Decomposition Reaction

-one compound breaks down or decomposes into two simpler compounds

-the reverse of synthesis

ex- 2H2O 2H2 + O2

Try these!!

a) lead(IV) oxide b) hydrogen iodide c) hydrogen bromide d) sodium chloride

a) PbO2 Pb + O2

b) 2HI H2 + I2

c) 2HBr H2 + Br2

d) 2NaCℓ 2Na + Cℓ2

3) Single-Replacement Reactions

-one element replaces a second element in a compound

ex- 2K + CaO K2O + Ca

-whether one metal will replace another metal is determined by reactivity of the metal

activity series of metals- lists metals in order of decreasing reactivity

ex- Mg + Zn(NO3)2

*is Mg above Zn on the reactivity series?

Mg + Zn(NO3)2 Mg(NO3)2 + Zn

ex- Mg + Ag2SO4

Mg + Ag2SO4 MgSO4 + 2Ag

ex- Mg + LiNO3

-lithium is above magnesium

Mg + LiNO3 no reaction

-Halogens can replace each other in single-replacement reactions

-Reactivity decreases as you go down the halogen group

Try These!!

a) zinc + hydrogen sulfate b) chlorine + sodium bromide c) zinc + sodium nitrate d) iron(II) + lead(II) nitrate e) chlorine + sodium iodide

a) Zn + H2SO4 H2 + ZnSO4

b) Cℓ2 + 2NaBr Br2 + 2NaCℓ

c) Zn + NaNO3 no reaction

d) Fe + Pb(NO3)2 Pb + Fe(NO3)2

e) Cℓ2 + 2NaI I2 + 2NaCℓ

4) Double-Replacement Reactions

-involve an exchange of cations between two reacting compounds

ex- BaCℓ2 + K2CO3 BaCO3 + 2KCℓ

ex- FeS + 2HCℓ H2S + FeCℓ2

Try These!!

a) sodium hydroxide + iron(III) nitrate 3NaOH + Fe(NO3) 3 3NaNO3 + Fe(OH)3

b) barium nitrate + hydrogen phosphate 3Ba(NO3) 2 + 2H3PO 4 Ba3(PO4) 2 + 6HNO3

c) potassium hydroxide+hydrogen phosphate 3KOH + H3PO4 K3PO4 + 3H2O

d) hydrogen sulfate + aluminum hydroxide 3H2SO4 + 2Aℓ(OH)3 Aℓ2(SO4)3 + 6H2O

5) Combustion Reaction

-hydrocarbon combined with oxygen to produce carbon dioxide and water

ex- C6H6 + O2 CO2 + H2O

-to balance any combustion begin with 2 in front of CxHy

2C6H6 + 15O2 12CO2 + 6H2O

*if all divisible by 2 then reduce

Try These!!

a) C14H26 + O2 CO2 + H2O

b) C8H12 + O2 CO2 + H2O

Answers!

c) 2C14H26 + 41O2 28CO2 + 26H2O

d) C8H12 + 11O2 8CO2 + 6H2O

Summary of Reactions

1) Combination/Synthesis

R + S RS

2) Decomposition Reaction

RS R + S

3) Single-Replacement Reaction

T + RS R + TS

4) Double-Replacement Reaction

RS + TU RU + TS

5) Combustion Reaction

CxHy + O2 CO2 + H2O